As a result of improved construction techniques and materials, residential and commercial buildings are becoming increasingly sealed from the outdoor environment. Because of inadequate ventilation in such buildings, the indoor air can contain a variety of substances that pose a health risk to its occupants. For example, the air may contain a build up of carbon dioxide, carbon monoxide, and volatile organic compounds. Consequently, there is a trend toward increasing the use of ventilation systems in order to improve indoor air quality. Increased ventilation, however, can significantly increase the heating and cooling loads on a building's heating, ventilation, and air-conditioning (HVAC) system. For example, dwelling ventilation is thought to account for 33% to 50% of the space-conditioning energy used in the 75 million single-family households in the United States. This amounts to around 1.6 exajoules of energy (or 262 million barrels of oil) at an operating cost of about $4 billion annually.
To reduce the load of a building's HVAC system, conventional ventilation systems sometimes use compact heat exchangers to temper incoming outdoor air with exhaust air. These heat exchangers are sometimes referred to as enthalpy recovery heat exchangers or energy recovery heat exchangers, which belong to the class of equipment known as heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs). By using a heat exchanger in connection with a ventilation system, incoming outdoor air can be pre-cooled (during cooling season) or pre-heated (during heating season), thereby reducing the sensible portion of air conditioning and heating loads. If the heat exchanger can transfer latent heat in addition to sensible heat (i.e., a total enthalpy heat exchanger), the latent portion of cooling and heating loads (dehumidification and humidification, respectively) can similarly be reduced.
Conventional heat exchangers typically use finned-tubes, enthalpy wheels, or heat pipes to help increase the heat transfer between the incoming and outgoing airflows. The heat exchange surface of such conventional designs is ordinarily made from a material having a relatively high thermal conductivity, such as aluminum, copper, or steel. Moreover, conventional heat exchangers are designed to fit in confined areas near to or within a building's heating, ventilation, and air-conditioning (HVAC) unit without sacrificing any efficiency. For these reasons, conventional heat exchangers tend to be too expensive for most building applications. Accordingly, there is a need for a lower cost alternative heat exchanger.